A transmission system to conduct videoconferences between remote places via a network, such as the Internet, is becoming increasingly popular. In this transmission system, a videoconference is conducted by exchanging image and audio data between two or more transmission terminals. With recent development of broadband environments, transmission and reception of high-quality image and audio data is enabled and a videoconference in appropriate conditions closely resembling reality may be conducted between the remote places.
There is a case in which, when conducting a videoconference using a transmission terminal, a person concerned as an attendant of the videoconference employs an external input device, such as a PC (personal computer), in addition to the transmission terminal connected to a display device and also connected to another transmission terminal via a network, an image, such as meeting documents, is displayed on a display of the external input device discussed with the partner of the videoconference. In such a case, according to the related art, the external input device has transmitted display data of the image, currently displayed on the display of the external input device, to the other transmission terminal of the communication partner via, the network.
The attendant of the videoconference may share with the communication partner not only the image data and the audio data exchanged between the transmission terminals but also the display data of the image currently displayed on the display of the external input device.
In a case of an external input device which is capable of performing multitask operations, two or more images of areas (windows) generated by different tasks may be simultaneously displayed on a display device. In this case, providing a user with a capability of selecting the display data of one of the two or more images to be transmitted to the other transmission terminal of the partner of the videoconference would be convenient for the user, and therefore a technology for allowing the user to select the display data of one of the images is proposed. For example, see Japanese Laid-Open Patent Publication No. 2011-254453.
FIG. 40 shows an example of a screen displayed on a display device of an external input device disclosed in Japanese Laid-Open Patent Publication No. 2011-254453. As shown in FIG. 40, according to Japanese Laid-Open Patent Publication No. 2011-254453, a user may select one of two areas (a) and (b) of the screen appearing on the display device with a mouse cursor (c) and share the display data of the selected area of the screen with a communication partner of the video conference on the other transmission terminal.
However, Japanese Laid-Open Patent Publication No. 2011-254453 is silent as to switching between a state in which display data of a whole screen area of the screen is shared and a state in which display data of a specific area of the screen is shared. Hence, there is a problem that the user is unable to switch from the state in which the display data of the specific area is shared to the state where the display data of the whole screen area is shared (or vice versa).